[amsat-bb] Cross Country Sentry 10 Info

Les Rayburn les at highnoonfilm.com
Fri Aug 8 01:57:31 UTC 2014

First of all, I should state that I have no financial interest in the 
Cross Country Sentry 10 SDR, nor any ax to grind against competitors. 
But I have gotten some additional information from it's developer that I 
think will be of interest to VHF operators. Overall, this product sounds 
like a real winner for both weak signal and satellite operators. The 
ability to have output on all VHF bands from 6 Meters thru 1.2 GHz would 
be perfect for rovers, and really simplify station design for the rest 
of us.

Here are the comments I've received from Chris, G4HYG.

I'm also a VHF/UHF weak signal enthusiast so I appreciate your kind 

We are in the final development phase of the transceiver and are 
planning to start a KickStarter project in about a month to put the 
transceiver into production.

To give you an idea of the technology used in the transceiver the RF 
front end device is a PGA-103+ low noise amplifier with a LTC5584 as a 
mixer. The PA stage uses the new BLP10H610 device from NXP. This NXP 
device is due to be released this month so it should be available when 
we are ready to start production.

The transceiver will work at 222 and 902/903 MHz for U.S. customers. Our 
intention is to supply different firmware and filter options depending 
on the customers location. For example the E.U., U.S, and Japan have 
different frequency specifications for imported amateur radio equipment. 
For in-house testing and any potential military customers we do have 
wideband firmware but I wouldn't like to release that firmware for 
general use for obvious reasons.

The approach we have taken with our existing SDR receivers is to try to 
design them so that they can use as many SDR programs as possible. The 
Sentry transceiver is somewhat different in that it doesn't divide the 
LO frequency by 4 to generate the 90 degree phase shift for the IQ LO 
injection. Programs will have to use the direct LO frequency without 
division. So far HDSDR and Quisk are the only programs I know of so far 
that will operate directly with the Sentry transceiver on both transmit 
and receive. SDR Radio and SDR Sharp work OK on receive. I'm in regular 
contact with most of the SDR software authors as I try to help them to 
add support for our products so I'll be in contact with them before 
launch to ask if they can add support for the Sentry transceiver.

Regarding the question about bandwidth the internal sound card has a 48 
kHz sampling rate so the span bandwidth is limited to 48 kHz, The 
transceiver will have a IQ output to drive external sound cards up to 
192 kHz. The transceiver is designed as a near zero IF (typically 100 Hz 
to avoid the AM and FM carrier appearing at DC). This helps prevent hams 
unintentionally transmitting out of band. The transmitter IQ chain is 
filtered with a 8.5 kHz filter to reduce the wideband noise that can be 
transmitted along with the wanted signal. We realize that many users 
will want to drive external high power amplifiers and transverters.

Recently I've been testing one of the the prototype transceivers during 
the weekly Tuesday night 4, 6, 2 and 70cm contests run by the RSGB. My 
local club (Bolton Wireless Club) have around 25 members who take part 
in the contest and as they are line of sight with my station it's a 
tough test of any receiver or transmitter during the contest. The latest 
tests have even included using unmatched antennas such as a HF dipole as 
a VHF antenna to see how the RF filtering worked in extreme mismatch 
conditions. A lot of the development time over the last two years has 
been dedicated to ensuring that the receiver is as good as we can make 
it and that the transmitter is clean with regard to wideband noise. All 
these on-air tests confirmed what had already been proved in the lab 
tests and proved that the design is good and now ready for production.

The original YouTube video and the photographs on the web page show an 
early prototype. The production version will have a different case more 
suited to fitting underneath a laptop PC. We are planning to add a new 
video showing a working prototype in action in a week or two.

Thanks for your kind comments about the plan for a KickStarter project. 
I'll update the web page and the CCW Yahoo group forum with regular 
progress reports.


Chris, G4HYG



Les Rayburn, N1LF
121 Mayfair Park
Maylene, AL 35114

6M VUCC #1712
AMSAT #38965
Grid Bandits #222
Southeastern VHF Society
Central States VHF Society Life Member
Six Club #2484

Active on 6 Meters thru 1296, 10GHz & Light

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